Bowling pinspotting machine sweep mechanism with drive means comprising distortable parallelograms



Nov. 10, 1964 s. FRIED 3,156,466

BOWLING PINSPOTTING MACHINE SWEEP MECHANISM WITH DRIVE MEANS COMPRISING DISTORTABLE PARALLELOGRAMS Filed May 18, 1962 3 Sheets-Sheet 1 FIGJ' INVENTOR GEORGE FRIED ATTORNEY Nov. 10, 1964 G. FRIED 3,156,466

BOWLING PINSPOTTING MACHINE SWEEP MECHANISM WITH DRIVE MEANS COMPRISING DISTORTABLE PARALLELOGRAMS Filed May 18, 1962 3 Sheets-Sheet 2 INVENTOR GEORGE FRIED w zwm.

ATTORNEY Nov. 10, 1964 G. FRIED BOWLING PINSPOTTING MACHINE SWEEP MECHANISM WITH DRIVE MEANS COMPRISING DISTORTABLE PARALLELOGRAMS 3 Sheets-Sheet 3 Filed May 18, 1962 IN VEN TOR.

GEORGE FRIED ATTORN EY United States Patent 3,156,466 BOWLING PTNSPO'ITHJ G MACHINE SWEEP MECH- ANISM WITH DRIVE MEANS CGMPRISING DIS- TORTABLE PARALLELOGRAMS George Fried, Stamford, Conn, assignor to American Machine 8; Foundry Company, a corporation of New Jersey Filed May 18, 1962, Ser. No. 195,925 6 Claims. (Cl. 273-54) This invention relates to bowling alley apparatus and,

more particularly, to an improved sweep apparatus esecially suited for use with modern bowling pin spotting machines for removing fallen pins from the alley bed.

It has become common practice, particularly in bowling alleys equipped with automatic pin spotting machines, to employ automatically controlled, power operated sweep apparatus for removing the fallen pins, and numerous such devices have heretofore been proposed. Such devices usually employ a sweep mounted to extend transversely of the alley bed and arranged for movement both vertically, so that the sweep can occupy an inactive, raised position, and horizontally, so that the sweep can be moved rearwardly over the alley bed to remove the fallen pins and then forwardly during its return travel. Since both substantially vertical and horizontal movements must be imparted to the sweep, the apparatus necessarily employs a reasonably complicated mechanical movement interposed between the drive motor and the sweep, and there has been a continuing need in the trade for improved sweep apparatus of this general type.

Recently, the problems encountered in developing satisfactory sweep apparatus have been made more severe because the vertical space available for such equipment in the bowling alley installations has been decreased. Thus, new bowling pin spotting machines have been so constructed as to have an especially low silhouette, with components such as the sweep apparatus necessarily compressed into a relatively short vertical space. On the other hand, the sweep itself must still be moved horizontally, in a substantially straight-line path, over the alley bed through the same relatively long distance always required heretofore by the position of the pit and the extent of the spotting area on the bed where fallen pins may come to rest. It is thus obvious that the already diflicult requirements for the working parts of the sweep apparatus have been made much more severe.

A general object of the invention is to provide an improved bowling alley sweep apparatus.

Another object is to devise such an apparatus which, though requiring substantially less vertical space than has heretofore been needed, is capable of moving the sweep in a straight-line fashion horizontally over a relatively large area of the alley bed.

A further object is to provide an apparatus of the type described which is especially stable and dependable in operation.

Yet another object is to provide such an apparatus which will be effective to sweep from the alley bed any fallen pin which happens to be so located on the alley bed as to lie beneath the sweep when the sweep descends to commence its horizontal travel over the alley bed.

In order that the manner in which these and other objects are achieved in accordance with the invention can be understood in detail, reference is had to the accompanying drawings, which form a part of this specification, and wherein:

FIGURE 1 is a side elevational view of a sweep apparatus constructed in accordance with one embodiment of the invention the sweep being shown in solid lines in its raised, inactive position and in dotted lines in its ex- 3,156,456 Patented Nov. 10, 1964 treme back position and in solid lines in its guard position;

FIGURE 2 is a front elevational view, with parts removed and broken away for clarity, of the apparatus of Figure 1;

FIGURE 3 is a fragmentary plan elevational view of a portion of the apparatus of FIGURE 1; and

FIGURE 4 is a partial side elevational view illustrating the relationships of parts of the apparatus during the sweeping action when a fallen pin happens to lie beneath the sweep as it descends.

Referring now to the drawings in detail, it will be seen that the embodiment of the invention chosen for illustration is shown as applied to a conventional bowling alley having a playing bed B, gutters G, kickbacks K and pit P, all arranged in the usual manner. The sweep apparatus of the invention is mounted on a frame P which in most instances forms part of the bowling pin spotting machine with which the sweep apparatus is usually associated. Frame F includes two longitudinally extending base members 10, each fixed to the top of a different one of the kickbacks, as by mounting brackets 11, and two longitudinally extending top members 12 each lying in the same vertical plane as a different one of base members 10. Members 10 and 12 are connected by rear uprights 13, forwardly slanting front members 14, and intermediate uprights 15, the latter being spaced forwardly from the pit a suitable distance, such as about one third of the length of the area of the alley bed over which the sweep is to travel horizontally.

Adjacent each kickback is a straight-line mechanism indicated generally at 16, the two mechanisms being identical. Each straight-line mechanism 16 comprises four links 17-20, all of equal effective length, pivoted together in quadrangular fashion. Thus, the upper end of link 17 is pivoted to the lower end of link 18 at 21; the upper ends of links 18 and 19 are pivoted together at 22; the lower end of link 19 is pivoted to the upper end of link 20 at 23; and the lower ends of links 20 and 17 are pivoted together at 24. Pivots 21-24 can be constructed in any suitable conventional fashion and provide mutually parallel pivotal axes at right angles to the plane of the linkage.

Each straight-line mechanism 16 also comprises a pair of supporting links 25 and 26 which have equal effective lengths and are substantially longer than links 17-20. Links 25 and 26 for each mechanism 16 are supported at their upper ends by a common pivot shaft 27 carried by bearing 28 which is secured to the corresponding frame member 12, shaft 27 being parallel to the axes of pivots 21-24. The lower ends of links 25 and 26 are pivotally connected to the parallelogram defined by links 17-20, supporting link 25 being connected to pivot 21 and supporting link 26 being connected to pivot 23.

A telescopic, collapsible and extensible link 29 has one end pivotally connected to the parallelogram of links 17-20 at pivot 22, the other end or the inner portion 33 of link 20 being pivotally mounted by a pivot shaft 30 journalled in a combined bearing and guide cam member 31 attached to upright 15. The outer portion 32 of link 29 is connected to pivot 22, while the inner portion of the telescopic link 29 is connected directly to pivot shaft 30 as explained hereinafter, link 29 functions as a control link, acting in compression to cause progressive distortion of the parallelogram defined by links 17-20 as the mechanism moves between positions II and III, FIG- URE 1.

Both straight-line mechanisms 16 are powered from a single electric drive motor 35 equipped with a right angle gear head 36 so that, while the motor is supported in vertical position by horizontal cross frame member 37, the output shaft 38 projects horizontally. Journalled in bearings 39 mounted on frame member 37 is a horizontal rock shaft 40 which extends transversely across frame F. Two levers 41 depend from rock shaft 40, each beside a different one of straight-line mechanisms 16. A crank 42 is fixed to output shaft 38. A link 43 has one of its ends pivoted to the end of crank 42 and the other pivoted to one of the levers 41. A drive link 44 is provided for each straight-line mechanism 16, one end of link 44 being pivoted to a lever 41 while the other end is pivoted to the corresponding supporting arm or link 25.

Continuous rotation of crank 42 causes oscillation of levers 41 about the axis of rock shaft 40 and this oscillatory motion is in turn imparted to the straight-line mechanisms 16 by drive links 44.

For each straight-line mechanism 16, there is fixed to link 17, near pivot 24, a suitable metal bracket 4-5 having a vertical body 46 through which extend two mounting bolts 47. These bolts secure a fiat metal or plastic bar 47A to web 51 described more in detail below. The sweep, indicated generally at 48, includes an elongated upper horizontal member 49, which is of U-shaped transverse cross-section, with the U inverted. To each end of member 49, there is secured an integral member 50 which both forms an end of the sweep structure and acts as a gutter paddle. Each member 50 comprises a fiat vertical web 51 which is at right angles to member 49 and has a rectangular top embraced by and rigidly secured to the corresponding end of member 49. Web 51 also projects rearwardly, including a portion 52 to which is bolted a flat vertical plate 53 having a slot 54. The bars 47A secured by bolts 4-7 to web 51 extend through slots 54. This arrangement allows sweep 48 to move upwardly and prevent breakage of parts, if for example the sweep should come down upon a pin in the position shown in broken lines in FIGURE 4. slides upwardly on bars 47A and damage is prevented.

Horizontal webs 55, extending parallel to member 49, project from each side of web 51, as shown in FIGURE 2. A rim portion 56, extending as part of a cylinder, integrally joins the ends of webs 55 and the bottom of web 51. A second upwardly extending flat web 57 projects from the end of the innermost horizontal web 55 to terminate in a rectangular top embraced by and fixed to member 49. Webs 51 and 57 are provided with horizontally aligned pairs of openings in which are fixed the end portions of parallel, horizontal sweep rods 58. From FIGURES l and 2, it will be seen that sweep 48 is so constructed and arranged that, with straight-line mechanism 16 lowered, the lower rod 58 thereof extends across the alley bed just above the surface thereof and portions 55 and 56, together with the lower portion of web 51, for each member 50 are centered in the corresponding gutter.

From FIGURE 2 in the embodiment of the invention illustrated herein, it will be seen that links 17-20 and supporting links 25 and 26 are so constructed that, when assembled, all of these links lie substantially in a common plane. Thus, the lower ends of links 17 and 18 are bifurcated, and the upper ends of links 19 and 20 are bifurcated, the other ends of the links being plain, and each plain end being received in the bifurcated end of the corresponding link, so that the main bodies of the links lie in a common plane. The lower ends of links 25 and 26 are bifurcated, straddling the parallelogram links 17-20 at pivots 21 and 23, respectively. The upper end of link 25 is bifurcated and straddles the plain upper end of link 26 at shaft 27, so that the bodies of links 25 and 26 lie in the same plane as the bodies of the parallelogram links.

The common plane of links 17-20 and 25, 26 is vertical and spaced slightly inwardly from the adjacent kickback and upright frame portions. Member 31, being mounted on upright 15, is located on the outer side of the vertical plane of the links, and telescopic link 29 thus extends adjacent to the outer side of the link assembly and slants slightly inwardly. Levers 41 are located each adjacent the inner side of one of the straight-line mechanisms, and

In such case, sweep 48 3' drive links 44 slant outwardly to their points of connection to links 25. The pivotal connections between link 29 and pivot 22, and at each end of drive link 44, are universal connections, as will be evident from FIGURE 2, and can be of any conventional type.

Combined bearing and guide cam member 31, as best seen in FIGURES l and 3, is in the form of a casting having a mounting base 59, engaged with intermediate upright 15, and a vertical web 68. Web 66 carries bearing 61 and an arcuate guide cam flange 62 which extends about a horizontal axis transverse to the frame F. Guide cam flange 62 extends through approximately below bearing 61 and has a free nose directed toward the front of the apparatus.

The end of Outer portion 32 of telescopic link 29 nearest member 31 is provided with a laterally projecting lug 63. When link 29 is collapsed to its shortest length position, lug 63 is disposed to travel within the arcuate space subtended by arcuate flange 62, as will be clear from FIGURE 1. If telescopic link 29 be extended, however, lug 63 is shifted to a position outside of the arc defined by flange 62 and will travel beneath the flange, as will be clear from FIGURE 4.

The central web of supporting link 25 has mounted thereon an axially adjustable stop screw 64 directed toward the central web 65 of link 18, the location of the stop screw and web 65 being such that, when the sweep is in its guard position II, tr e tip of screw 64 is engaged with web 65. If the straight-line mechanism is caused to swing upwardly and forwardly from the guard position to its dwell or inoperative position I, then screw 64 engages web 65 which coact to prevent further collapse of the parallelogram defined by links 17-20. Since the parallelogram is held against collapsing, and since supporting links 25 and 26 are of fixed length, sweep 48 travels an arcuate path as it moves between the guard and elevated positions I and II, this path being centered on the axis of shaft 27, telescopic link 29 extending as the sweep is raised and contracting as the sweep is lowered. Thus, the combination of screw 64 and web 65, along with the telescopic nature of link 29, allows the output end of the straight-line mechanism to travel an arcuate, rather than a straight-line path when the apparatus operates to raise or lower the sweep.

Sweep motor 35 is operated to effect a controlled movement of sweep 48 to and from, and along alley bed B in timed relationship with the movement of a suitable pin spotting and respotting apparatus (not shown) which may be similar in construction and operation to that shown in co-pending Congelli and Hays application for Pin Spotting and Rcspotting Mechanism, S.N. 195,926, filed May 18, 1962, or of the type shown in Dumas Patent 2,890,886. The sweep, in its normal operation, is moved from the inactive raised dwell position I to the guard position II, this being the initial operative position of the sweep at the alley bed, and thence along alley bed B to the rearward, pin discharge position III where pins are discharged into pit P. The controlled operation of motor 35 is effected by means of several control cams, designated generally C, mounted on shaft 38 and switches coacting therewith, designated generally S, in the motor control circuit of the machine (not shown) of which the sweep 48 and its mechanism forms a part. Since the control is not a specific part of the invention, further description and showing thereof are omitted. Reference is made, however, to copending Blewitt application S.N. 195,927, filed May 18, 1962, for control mechanism for bowling pin spotting machine, and also to Dumas Patent 2,890,886 which disclose control means suitable for use in operating sweep motor 35.

When motor 35 is operated in a direction to drive the straight-line mechanism arcuately downward toward the alley bed, the parallelogram defined by links 17-20 does not change in shape, since telescopic control link 29, having been extended, contracts progressively as the sweep 48 approaches the alley bed. When the sweep reaches.

its lowered position, illustrated in FIGURES 1 and 2, link 29 has become fully contracted, with lug 63 disposed to travel above cam flange 62. Further operation of the drive motor 35 positively swings supporting link 25 rearwardly. 'The parallelogram defined by links 17-20 now distorts progressively, as will be clear from FIGURES l and 4, the angles subtended by links 18, 19 and links 20 and17 progressively increasing. The length of link 29 remains substantially unchanged and the distance of pivot point 24 above the alley bed, and therefore the distance of the sweep above the alley bed, remains substantially constant. When the straight-line mechanism swings past the vertical, supporting link 26 progressively approaches link 25 and the parallelogram defined by links 17-20 progressively distorts to decrease the angles subtended by links 18, 19 and 20, 17. Thus,

once the straight line mechanism has fully lowered the sweep, it operates to move the sweep essentially horizontally until all of the fallen pins have been swept into pit P. The operation of driving motor 35 now causes a reversal of the complete operation just described, with the sweep being returned back to its initial position adjacent the alley bed and then, if the motor continues to rotate, being raised arcuately to the inactive position shown in FIGURE 1. It will be understood that drive motor 35 can be automatically controlled to program the sweep through any desired series of movements. Thus, for example, the apparatus can be operated to lower the sweep and then to raise the sweep without going through the horizontal sweeping cycle.

Considering FIGURE 4, and recognizing that the length of control link 29 remains substantially unchanged as the straight-line mechanism travels between positions II and III, it will be apparent that the length of the diagonal defined by pivot points 22 and 24 decreases to a minimum as the sweep passes below shaft 27. Further, the nature of the straight-line mechanism is such that at no stage of the operation does any part of the mechanism project above the level of shaft 27. Accordingly, the nature of the straight-line mechanism employed is such that a minimum of vertical space above the alley bed is required.

Though most of the fallen pins P come to rest on the area of the alley bed B over which sweep 48 is moved horizontally, it occasionally happens that a pin comes to rest in that particular area approached by the sweep as it is lowered. Thus, this pin is illustrated in such position in FIGURE 4. Since the maximum diameter of the bowling pin is substantially greater than the vertical distance between the alley bed and the lowermost one of rods 58 of the sweep, it is obvious that the sweep will engage this pin before the sweep completes its downward travel. Therefore, sweep 43 must stop at a time when the straight-line mechanism is still traversing that portion of its travel which would normally complete movement of the sweep toward the alley bed. Normally, in this type of situation, sweep 48 will slide upwardly relative to the pin because of the sliding support provided by bars 47A and slots 54 of plates 53.

Were this fallen pin not in the way, and in the normal operation, as described, final arcuate movement of sweep 48 toward the alley bed would occur without distortion of the parallelogram defined by links 17-20, stop screw 64 being in engagement with web 65, and telescopic link 29 progressively contracting. However, when the lowermost one of sweep rods 58 engages this pin, if for any reason bars 47A do not slide upwardly in slots 53 in plates 54, as in the case of a bind, the effect is as if the length of telescopic rod 29 were then rigidly fixed, so that further swinging movement of supporting link 25 causes the angles subtended by links 18, 19 and 20, 17 to increase. The straight-line mechanism now functions to move sweep 48 horizontally rearwardly, with this bowling pin positively engaged between the lowermost rod 58 and the surface of the alley bed (see FIGURE 4). The pin is, therefore, positively dragged along toward the pit, sliding along the surface of the alley bed. Other fallen pins disposed rearwardly of the initial lowered position of the sweep are also swept into the pit, since the space between the lowermost rod 58 and the surface of the alley bed is too small to pass the pins.

Noting that the effect of engagement of the sweep with this bowling pin is to stop the progressive contraction of the link 29, it will be understood that lug 63 retains its position, so that, as the rearward motion of the sweep continues, lug 63 passes beneath arcuate cam flange 62. The spacing between flange 62 and the axis of bearing 61 is predetermined in such fashion that, during further operation of the sweep mechanism during the cycle under consideration, the effective length of link 29 cannot be shortened more than would cause the lowermost rod 53 to approach to a point above the alley bed equal approximately to the maximum diameter of a bowling pin. The arrangement advantageously is such that, with the lowermost rod 58 engaging the portion of this pin of largest diameter, lug 63 will ride directly in contact with the lower face of flange 62 into cam slot 70. Lug 63 and flange 62 thus cooperate both to stabilize the mechanism under the circumstances illustrated in FIGURE 4, and to assure that jamming of the mechanism will not occur so that the pin engaged by rod 58 will be delivered into pit P.

While a particular embodiment of the invention has been chosen for illustrative purposes, it will be understood that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In a bowling alley sweep mechanism, the combination of two straight-line mechanisms each disposed at a different side of the alley bed and each comprising four links pivoted end-to-end to define a parallelogram, said links all having the same effective length, the pivot points between adjacent ones of said links defining the respective ends of the two diagonals of said parallelogram,

a pair of supporting l-inks each having one end pivotally connected to a pivot defining a different end of one of said diagonals,

support means disposed above the alley bed, the other ends of said supporting links being pivotally connected to said support means in such fashion that the combination of said sup porting links and said four links is suspended for pivotal movement lengthwise of the alley bed,

the parallelogram defined by said four links being disposed in a substantially upright plane so that the other diagonal thereof has one end nearer said support means than is the other end, and control means operatively connected at the pivot point defining said one end of said other diagonal;

a sweep having its end portions each connected to a different one of said straight-line mechanisms at said other end of said other diagonal; and

power means operatively connected to drive both of said straight-line mechanisms in synchronism through a cycle in which said supporting links first swing downwardly, from a forwardly raised position, toward the alley bed to bring said sweep to an initial operative position at the alley bed, then rearwardly through a predetermined angle to bring said sweep to a rearward position, and the forwardly in return to said forwardly raised position,

said control means of each of said straight-line mechanisms being operative in compression, during swinging of the supporting links through said predetermined angle, to restrict the path of travel of the pivot point defining said one end of said other diagonal to a predetermined are such that the parallelograms defined by said four links of each straight-line mechanism are progressively distorted to maintain said sweep in substantially straight-line horizontal movement as said sweep travels between said initial operativc position and said rearward position, the length of said other diagonal of the parallelogram defined by said four links of each of said straight-line mechanisms being smaller as said supporting links of said straight-line mechanisms swing through the central portion of said predetermined angle than when said sweep is at said initial operative position and said rearward position, whereby the vertical space required for the sweep mechanism is minimized. 2. A sweep mechanism in accordance with claim 1 and wherein said control means comprises a collapsible and extensible link having one of its ends pivoted to a fixed point and the other of its ends pivoted at the pivot point defining said one end of said other diagonal. 3. A sweep mechanism in accordance with claim 2 and wherein each of said straight-line mechanisms comprises stop means operatively associated with at least one of said four links to fix said four links against movement relative to each other when said supporting links have been swung forwardly through said predetermined angle, further forward pivotal movement of said supporting links causing said straight-line mechanisms to move said sweep upwardly to a raised inactive position. 4. A sweep mechanism in accordance with claim 3 and wherein said stop means for each of said straight-line mechanisms comprises a pair of elements disposed for mutual abutting engagement, one of said elements being carried by one of said supporting links and the other of said elements being carried by the adjacent one of said four links. 5. A sweep mechanism in accordance with claim 2 and wherein said collapsible and extensible link is telescopic, the sweep mechanism further comprising stop means carried by one telescopic section of said collapsible and extensible link, and an arcuate guide member mounted to extend about the fixed point to which said one end of said collapsible and extensible link is pivoted, said arcuate guide member extending through only a portion of said predetermined angle,

said stop means being engagcable with said arcuate guide member to ride therealong when said sweep encounters a fallen bow-ling pin as said sweep is swung downwardly toward said initial operative position. 6. In a bowling alley sweep mechanism, the combinafour links pivoted end-to-end to define a parallelogram, said links all having the same effective length so that the four sides of the parallelogram are all equal, the pivot points between adjacent ones of said links defining the respective ends of the two diagonals of the parallelogram,

a pair of supporting links each having one end pivotally connected to the pivot point defining a different end of one of said diagonals, said supporting links having effective lengths equal to each other,

support means disposed above the alley bed, the

other ends of said supporting links being pivotally connected to said support means for movement about a common horizontal axis,

the parallelogram defined by said four links being disposed in a substantially upright plane so that the other diagonal thereof has one end nearer said common horizontal axis than is the other end, and

control means operatively connected to said four links;

a sweep having its end portions each connected to a different one of said straight-line mechanisms at said other end of said other diagonal; and

power means operatively connected to drive both of said straight-line mechanisms in synchronism through a cycle in which said supporting links first swing downwardly, from a forwardly raised position, to- Ward the alley bed to bring said sweep to an initial operative position at the alley bed, then rearwardly through a predetermined angle to move said sweep to a rearward position, and then forwardly in return to said forwardly raised position,

said control means for each of said straight-line mechanisms being constructed and arranged to act in compression on the combination of said four links of the straight-line mechanism to progressively distort the parallelogram defined by said four links in such fashion that said other diagonal is progressively shortened as said sweep moves rearwardly toward a point below said common horizontal axis and is progressively lengthened as said sweep then continues its travel to said rearward position, whereby said sweep is maintained in substantially straightline horizontal movement as said sweep travels between said initial operative position and said rearward position, and the vertical space required for the sweep mechanism is minimized.

References Cited in the file of this patent UNITED STATES PATENTS tion of 2,911,218 Scherzinger Nov. 3, 1959 two straight-line mechanisms each disposed at a differ- 2,942,884 Scherzinger June 28, 1960 ent side of the alley bed and each comprising 2,992,827 Harper July 18, 1961 

1. IN A BOWLING ALLEY SWEEP MECHANISM, THE COMBINATION OF TWO STRAIGHT-LINE MECHANISMS EACH DISPOSED AT A DIFFERENT SIDE OF THE ALLEY BED AND EACH COMPRISING FOUR LINKS PIVOTED END-TO-END TO DEFINE A PARALLELOGRAM, SAID LINKS ALL HAVING THE SAME EFFECTIVE LENGTH, THE PIVOT POINTS BETWEEN ADJACENT ONES OF SAID LINKS DEFINING THE RESPECTIVE ENDS OF THE TWO DIAGONALS OF SAID PARALLELOGRAM, A PAIR OF SUPPORTING LINKS EACH HAVING ONE END PIVOTALLY CONNECTED TO A PIVOT DEFINING A DIFFERENT END OF ONE OF SAID DIAGONALS, SUPPORT MEANS DISPOSED ABOVE THE ALLEY BED, THE OTHER ENDS OF SAID SUPPORTING LINKS BEING PIVOTALLY CONNECTED TO SAID SUPPORT MEANS IN SUCH FASHION THAT THE COMBINATION OF SAID SUPPORTING LINKS AND SAID FOUR LINKS IS SUSPENDED FOR PIVOTAL MOVEMENT LENGTHWISE OF THE ALLEY BED, THE PARALLELOGRAM DEFINED BY SAID FOUR LINKS BEING DISPOSED IN A SUBSTANTIALLY UPRIGHT PLANE SO THAT THE OTHER DIAGONAL THEREOF HAS ONE END NEARER SAID SUPPORT MEANS THAN IS THE OTHER END, AND CONTROL MEANS OPERATIVELY CONNECTED AT THE PIVOT POINT DEFINING SAID ONE END OF SAID OTHER DIAGONAL; A SWEEP HAVING ITS END PORTIONS EACH CONNECTED TO A DIFFERENT ONE OF SAID STRAIGHT-LINE MECHANISMS AT SAID OTHER END OF SAID OTHER DIAGONAL; AND POWER MEANS OPERATIVELY CONNECTED TO DRIVE BOTH OF SAID STRAIGHT-LINE MECHANISMS IN SYNCHRONISM THROUGH A CYCLE IN WHICH SAID SUPPORTING LINKS FIRST SWING DOWNWARDLY, FROM A FORWARDLY RAISED POSITION, TOWARD THE ALLEY BED TO BRING SAID SWEEP TO AN INITIAL OPERATIVE POSITION AT THE ALLEY BED, THEN REARWARDLY THROUGH A PREDETERMINED ANGLE TO BRING SAID SWEEP TO A REARWARD POSITION, AND THE FORWARDLY IN RETURN TO SAID FORWARDLY RAISED POSITION, SAID CONTROL MEANS OF EACH OF SAID STRAIGHT-LINE MECHANISMS BEING OPERATIVE IN COMPRESSION, DURING SWINGING OF THE SUPPORTING LINKS THROUGH SAID PREDETERMINED ANGLE, TO RESTRICT THE PATH OF TRAVEL OF THE PIVOT POINT DEFINING SAID ONE END OF SAID OTHER DIAGONAL TO A PREDETERMINED ARC SUCH THAT THE PARALLELOGRAM DEFINED BY SAID FOUR LINKS OF EACH STRAIGHT-LINE MECHANISM ARE PROGRESSIVELY DISTORTED TO MAINTAIN SAID SWEEP IN SUBSTANTIALLY STRAIGHT-LINE HORIZONTAL MOVEMENT AS SAID SWEEP TRAVELS BETWEEN SAID INITIAL OPERATIVE POSITION AND SAID REARWARD POSITION, THE LENGTH OF SAID OTHER DIAGONAL OF THE PARALLELOGRAM DEFINED BY SAID FOUR LINKS OF EACH OF SAID STRAIGHT-LINE MECHANISMS BEING SMALLER AS SAID SUPPORTING LINKS OF SAID STRAIGHT-LINE MECHANISMS SWING THROUGH THE CENTRAL PORTION OF SAID PREDETERMINED ANGLE THAN WHEN SAID SWEEP IS AT SAID INITIAL OPERATIVE POSITION AND SAID REARWARD POSITION, WHEREBY THE VERTICAL SPACE REQUIRED FOR THE SWEEP MECHANISM IS MINIMIZED. 